LT1952
20
1952f
APPLICATIO S I FOR ATIO
WUU
U
Figure 14. 36V to 72V Input to 5V at 20A Synchronous Forward Converter
Figure 13. Output Voltage Transient Response
(6A to 12A Load Step at 6A/µs)
Figure 12. LT1952-Based Synchronous Forward Converter
Efficiency vs Load Current (For Circuit in Figure 14)
LOAD CURRENT (A)
0
EFFICIENCY (%)
2520
1952 F12
5
10
15
98
96
94
92
90
88
86
V
IN
= 48V
V
OUT
= 5V
f
OSC
= 300kHz
V
DD
CG
PGND
GND
OPTO
V
COMP
V
FB
FG
SYNC
V
AUX
I
COMP
+I
SNS
–I
SNS
OVP
LTC1698
1
2
3
4
5
6
8
16
15
14
13
12
11
9
HCPL-M453
0.1µF
10V
BIAS
6
5
4
1
2
3
SYNC
7V
BIAS
+V
0UT
R14
1.2k
R16
12.4k
R15
38.3k
C9, 6.8nF
1µF
X5R
R13
270Ω
0.1µF
T1
PA0491
Q2
PH3830
Q3
PH3830
L1
PA1393.152
C
01
100µF
X5R
2×
+V
0UT
5V
20A
SYNC
BAS516
220pF
560Ω
T2
SOUT
SOUT
C
IN
2.2µF
100V
X5R
+V
IN
36V TO 72V
1952 F14
Q1: PHM15NQ20 PHILIPS
SD_V
SEC
OUT
OC
I
SENSE
PGND
GND
V
IN
LT1952
BLANK DELAY
912
16
5
6
2
3
4
7
14
11
10
13
8
15
115k
1k
0.1µF0.1µF
10V
BIAS
475k
18.2k
22k
40k 33k 4.75k
9.53k
100k
Q1
0.015Ω
COMP
1
1µF
40k
SYNC
SOUT
SS_MAXDC
V
REF
FB
R
OSC
V
OUT
(200mV/DIV)
0A
I
OUT
(5A/DIV)
20µs/DIV
1952 F13